This study documents the use of prostitutes (commercial sex workers) by new male patients attending a genito urinary medicine clinic. 541 consecutive male patients completed an anonymous self-administered questionnaire. 48 (8.9%) gave a history of previous purchase of sexual services in Northern Ireland and/or elsewhere; 69% of these encounters occurred outside Northern Ireland. The largest group were single men aged 20-29 years. 87% of those who purchased services in Northern Ireland were asked by the prostitute to use a condom compared with 60% elsewhere, but there was no significant difference in actual condom use between both groups (66.7% vs 72.7%) Only 21% of patients who had purchased the services more than once used condoms consistently and 29% were willing to pay more for unprotected sexual intercourse. 40% attributed their attendance at this clinic directly or indirectly to their encounter with a prostitute. Encounters with prostitutes were often related to alcohol consumption, 88% sometimes or always purchasing these services after drinking alcohol. Despite widespread publicity at-risk behaviour involving unprotected sexual intercourse with prostitutes is not uncommon. Health education should be targeted at the young single male who travels outside Northern Ireland.